Thread: Cross-connection of water softener drain

I see some things so often that I think are wrong, that occasionally I have to double-check myself. My understanding is that backwash drain lines from water softeners and other water treatment devices such as iron filters must drain into a floor drain or similar place, but if they drain into the DWV (domestic drain, waste, vent) system it needs to have an air gap and a p-trap. True? Is it sufficient to drain into a standing pipe on a drainpipe with a p-trap, or must it also have an air trap? Is it either an air gap, or a p-trap, or both?

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You are correct. An air gap or an air break is necessary to prevent water contamination.